1. Field
The present invention relates to structural and aerodynamic aircraft parts. More particularly, the present invention relates to material dispensing and compaction, such as composite tape automated fiber placement (AFP).
2. Related Art
Fiber placement is a method of compacting a resin-impregnated composite material, also referred to as prepreg tow, onto a surface of an item such as a tool surface, mold, mandrel, or any surface used to form composite parts. In a typical fiber placement method, multiple layers of the composite material are compacted together and cured to form a strong, light-weight component of a pre-determined shape for use in the construction of aircrafts, missiles, satellites, automobiles, etc.
According to traditional fiber placement methods, multiple pieces of composite material are typically compacted simultaneously to the surface using one larger roller or segmented roller which rotates on a single shaft. However, since the roller or roller segments rotate around a single shaft, compacting material onto the surface over sharp angles or complex contours is challenging. For example, as a wide roller or a segmented roller rolls over certain complex contours, a portion of the roller makes no contact against the surface, and a portion of the tape is not compacted. The portion of the material that is not compacted can result in delamination or porosity of the cured part formed by the material.
After dispensing and compacting material onto the surface in one direction, traditional fiber placement machines reverse directions by rotating an entire material placement head 180°. For example, in a typical application, a material placement head dispenses and compacts material onto a surface in one direction, then cuts the material. After this, the material placement head continues traveling a specified roll-off distance and then retracts from the surface. Then the material placement head rotates 180°, reapproaches the surface, engages the surface, and dispenses and compacts the material to the surface, traveling in the opposite direction. Because of the many thousands of strands required for a typical composite part, this retract-rotate-reapproach method can add a significant amount of time to the material application process.
Current rollers known in the art for compacting composite material are flat from edge to edge. Therefore, in order to apply an equal amount of pressure to an entire strip of tape during compaction, the roller must remain perpendicular to the surface. This can be challenging or sometimes impossible to achieve depending on the complexity of the contours required for a given part.
Accordingly, there is a need for an improved method of dispensing and compacting material to a surface that does not suffer from the problems and limitations of the prior art.